In recent years, an increase in allergic diseases has been noted and it is reported that, in about one-third of the newborn babies, onset of atopic dermatitis or asthma is observed. A drastic increase in onset of pollinosis has been becoming a big social problem as well.
It has been believed that changes of environment surrounding us such as westernization of meals, air pollution, food additives and excessive stress are the causes of an increase in such allergic symptoms.
In view of the immunological competent cell and immunoglobulin which are participated therein, allergic reaction is classified into from type I to type IV. Diseases represented by allergic rhinitis and bronchial asthma belong to the allergic reaction of type I where IgE antibody is produced in large quantities when exposed to allergen and chemical mediators such as histamine, leukotrienes and prostaglandin are produced and released from mast cells and basophils via the said IgE antibody whereby dilation of blood vessel, promotion of blood vessel permeability, shrinking of bronchial smooth muscles, stimulation of nerve terminals, etc. are induced. Therefore, for the therapy of allergic diseases of type I, antihistaminic agents and antiallergic agents having an action of suppressing the liberation of chemical mediators from mast cells have been used.
However, antihistaminic agents and basic antiallergic agents have adverse actions such as drowsiness, thirst, gastrointestinal troubles, etc. and their continuous administration for a long period causes a problem.
Allergic reaction of type IV is a reaction of a delayed type in which T cells are participated where T cells receiving an antigen information via antigen-presenting cells such as Langerhans cells and macrophage produce and release various cytokines whereby an inflammation reaction of a delayed type takes place due to accumulation of eosinophils and macrophages.
Allergic contact dermatitis is a typical disease which occurs due to an allergic reaction of type IV. Steroid agents are used for the therapy of allergic diseases of type IV and such steroid agents suppress the production of cytokine in T cells and show a dramatic effect for the therapy of eczema. On the other hand however, there is a possibility that they cause severe adverse actions such as a decrease in adrenocortical function, flushing of the skin, atrophy and dilation of capillaries by their administration for a long period.
In the meanwhile, tea is a typical luxurious beverage and has been drunk by many people during more than 2000 years. It has been also known that tea has various physiological functions and, for example, its antioxidative action, antitumor action, suppressive action to carcinogenesis, antibacterial action, antiviral action and anticarious action have been reported.
With regard to an allergic action, there have been exemplified the therapeutic agent to the allergic reaction of type I as an antiallergic agent mainly comprising an extract from oolong tea using an action of suppressing the histamine liberation from mast cells as an indicator in Japanese Patent Laid-Open No. 258726/1991; the effective cases of natural caffeine for the promoting reaction of blood vessel permeability in allergic symptom of type I in Japanese Patent Laid-Open No. 17865/1995; and therapeutic agents such as antiallergic agent, anti-inflammatory agent, anti-atopic dermatitis agent and anti-psoriasis where an extract of oolong tea is an effective ingredient in Japanese Patent Laid-Open Nos. 77231/1998 and 175874/1998.
It has been further reported that green tea catechins such as epigallocatechin gallate and epicatechin gallate suppress the liberation of histamine from mast cells in abdominal cavity of rat (Journal of Japanese Society for Food Science and Technology, Vol.42, No. 11, p. 952-958, 1955; and Allergy, Vol. 52, No. 1, pp. 58-64, 1997). However, there has been no report that polyphenols such as strictinin suppress the production of IgE by B cells which is an origin of allergic reaction.
Pharmaceutical agents for allergic diseases have been developed and used for the therapy already but, since they have adverse actions, there has been a strong demand for antiallergic agents derived from natural products where a long-term administration is possible, safety is high and no adverse reaction takes place.
Thus, an object of the invention is to provide a therapeutic and preventive agent for allergic diseases which has no adverse action, shows a high safety even by a long-term administration and is able to be utilized for food and/or beverage and cosmetic agent which are used daily.
In order to solve the above-mentioned problems, the present inventors have carried out a screening of substances having antiallergic action using a suppressive action for the production of IgE as an indication and have found that polyphenols such as strictinin exhibits such an effect and, based upon such a finding, the invention has been achieved.